Yasutsugu Takeda

Random phase shifters for fourier transformed holograms.

The random phase shifter method for Fourier transformed holograms is discussed. It is shown that by adopting the random phase shifters of the phase quantization levels beyond 2 (4, for example), the effectiveness becomes about twice that of 2, and that the reduction of the effectiveness by the coincidence between a pattern of the information and a phase shifter can be withdrawn under the probability of 10(-10). Hologram memories of information storage density of 10(5) bits/mm(2) and 2.0 x 10(3) characters/ mm(2) are demonstrated.

High density image-storage holograms by a random phase sampling method.

The random phase sampling method that has been proposed to make high quality and high storage density holograms capable of storing image information is described and discussed from the aspect of the quantitative characteristics of its reconstructed image. The method enables the uniform distribution of light energy over the hologram area made on the exact Fourier transformed plane. The details of the characteristics of the method are investigated, especially with respect to the luminance tone linearity, the signal-to-noise ratio, and the resolution to give good agreement with the results of a calculation. In the experiment, reconstructed images with high quality were obtained from holograms of 2-mm diam, which were made by 10(6) sampling and random phase shifting. By using the random phase sampling medthod, an image retrievel model system storing twenty kinds information was developed. This system holds promise of being used in various practical applications such as holographic ultramicrofilm system or a holographic videopackage system.

Hologram Memory with High Quality and High Information Storage Density –Hologram Memory–

A hologram memory with the information storage density of 105 bits/mm2 is realized by the RPS (Random Phase Shifter) method. The storage density is in the region of the theoretical limit predicted from the characteristics of the optical system. It is visualized by experiments and numerical calculations that by the RPS method the hologram memory of higher quality and higher information storage density can be made than by the commonly used defocussing method. For the future target, hologram memory of storage density of 107 bits/mm2 is suggested through the considerations of the theoretical limit from the storage medium.

Holographic video disk: an alternative approach to optical video disks

Optical video disks employing time sequential coding are superior to mechanical video disks because of their noncontact reproducing capability. One drawback in the optical systems is the necessity of precise focusing and tracking adjustments. To solve this problem, an alternative approach, using a holographic technique that makes it possible to store a frame of information in a specified area redundantly, is proposed. A design concept and experiments relating to the breakthroughs are described. A combination of random phase sampling holography and coherently superimposing holography makes it possible to store color-encoded images sufficient for about a 30-min motion picture on a disk of 300 mm in diameter. A sound recording technique suitable for the holographic video disk, constituting one-dimensional hologram-type, pulse-coded-modulation signals, is proposed.

A managerial approach to research and development cost-effectiveness evaluation

An overall research and development (R&D) cost-effectiveness evaluation system that is currently in operation is described and discussed. Evaluation is done on several cross sections of R&D management. For use with several usage objectives of cost effectiveness, some variations of the figure of merit (FOM) are shown. The FOM indicates R&D danger symptoms, especially on promising future trunk-line products. The authors conclude that cost-effectiveness evaluation can be used strategically by taking into consideration the phase of research, the products life cycle, and future growth factors. Some prospects and analysis for future R&D are reviewed and discussed. >

Use of heterostructure diode lasers in video disk systems

The application of heterostructure lasers to video disk systems is described. The buried heterostructure diode laser is used as a light source of the optical pickup for the optical video disks. This pickup enables video signals to be reproduced with a SNR of more than 40 dB. These lasers can be not only used as a light source to read out the signal from the disk but also as a detector of the reflected light.

Semiconductor Laser Pickup for Optical Video Disk Player

Almost five years have passed since the concept of the optical video disk system was first presented, and several kinds of systems have been developed these few years. 1,2,3,4 Recently, the standardization of these confused optical video disks was made and optical video disk player systems have already reached the stage of commercial development.5 Optical video disk systems offer several advantages to mechanical and capacitive video disk systems. High image quality, still and slow motion picture capability are some of its chief attractions. Unfortunately, large, complicated, and expensive optical pickups still remain a problem. Part of the difficulties is the use of the He-Ne laser as a light source. Although the He-Ne laser is one of the most stable and compact gas laser among several commercial available lasers, its size, over 200mm length and 30mm in diameter, is still too large for a compact optical pickup. Moreover, high voltage power supply of over 1.5KV are not desirable for home use systems. In addition, the optical system used in the pickup is quite complex because separate laser beams are used to detect the auto-focusing signal, the tracking signal, and the video signal. These factors make for a very expensive overall cost in labor for manufacturing and maintenance.

Digital Spatial Modulators

Present situations of developments of digital spatial modulators are summarized and new models of the digital spatial modulators made of crystals of gadolinium molybdate are introduced. The first model is of a frame at a time mode. A principle of the design is based on the ferroelectric and ferroelastic properties of the crystal. The second model is of a line at a time mode. The developed models of 64 bits of a frame at a time mode and of 1152 bits of a line at a time mode are described with their experimental results of trials of writing holographic memories. The signal-to-noise ratio of 100 and 20 are obtained in the reconstructed images, respectively. Digital spatial modulators of thousands bits per frame with the data transfer rate of 100 kbits per second can be expected in their extensions.

Some experiences on HIVIPS-Hitachi visiting research programs

A description is given of the Hitachi visiting research programs (HIVIPS), which were designed to achieve reciprocal international collaborative research. Experience with the program is reported and research and development collaboration is discussed. Among the observations noted are these: the crucial factor in determining the degree of success is the personality of a visiting researcher, as well as his or her professional depth; the effectiveness of the research depends upon the quality of the responsible research colleague or supervisor of the visiting researcher; and more infrastructural and environmental factors influence the morale of a visiting researcher.<<ETX>>

Prospects for Superconducting Electronics

Information systems in the 21st century are spotlighted and superconducting electronics are stressed as one of the key technologies. Present status of superconducting electronics is reviewed with some historical backgrounds. “Quantum flux parametron” and three terminal devices are given as examples of 2nd generation technology in superconducting electronics. A tentative goal and the state of the art of high-Tc superconductors are summarized for superconducting LSIs at Liq. N2 temperature.